Computer for converting electrical code into shaft rotation



June 23, 1953 ELECTRICAL L. B. HALLMAN JR 2,543,355

I COMPUTER FOR CONVERTING CODE INTO ROTATION Filed June 15, 1951 4 Sheets-Sheet l INVENTOR.

June 23, 1953 L. B. HALLMAN, JR 2,543,355

COMPUTER FOR CONVERTING ELECTRICAL L CODE INTO $HAFT ROTATION Filed June 15, 1951 4 Sheets-Sheet 2 BY WW 8770 M5 at M [421: II. I

June 23, 1953 L. a. HALLMAN, JR 2,543,355

COMPUTER FOR CONVERTING ELECTRICAL CODE INTO SHAFT ROTATION Filed June 15, 1951 4 Sheets-Sheet 4 I z 5 g (a) n I i 5 E i 5 47 927 (a) H H i H a /dd0 i I I i (c) n E l l E I 5 200 9 H 3 5 FL i 5 i I E 4 Z J 4 5 7 I .9 /o /244 I 7/05 I wnh h? a '9 1 I 200 i E E (70 [L 5 E g 40 (9) 1 E 5 a 4 5 7 a M #45 P011! fdd/7/dh INVENTOR. JA? .1 5 7 ZflfiZfl/V.5 //fl [MW/V y Mu.

ATTOQ Vf/ Patented June 23, 1953 COMPUTER FOR CONVERTING ELECTRICAL CODE INTO SHAFT ROTATION Ludlow B. Hallman, Jr., Dayton, Ohio Application June 15, 1951, Serial No. 231,885

6 Claims.

(Granted under Title 35, U. S. Code (1952),

sec. 266) The invention described herein may be manufactured and used by or for the United States Government for governmental purposes without payment to me of any royalty thereon.

This invention relates to an electrical computing device for converting an electrical pulse-type code into revolutions of a shaft. The device finds particular usefulness in automatic landing systerns for aircraft in cases where it is desired to transmit runway elevation data to the airplane in the form of a shaft rotation, but it may be used in any application requiring a remote control of the total number of revolutions which a shaft has undergone as measured from the starting or zero revolution position of the shaft.

In brief the computer comprises an adjustable Wheatstone bridge, a shaft, and a plurality of parallel mechanical couplings between the shaft and the adjusting mechanism of the bridge. There are as many of these couplings as there are digits in the maximum desired number of revolutions of the shaft. Each of the couplings contains a gear box having a ratio related to the ratios of the other gear boxes in multiples of ten, in the same manner that the places of a decimal number are related. The desired number of revolutions of the shaft is transmitted to the computer in the form of successive electrical codes representing the digits of the decimal number corresponding to the number of revolutions. In response to each code transmission the computer couples the shaft to the bridge adjusting mechanism through the appropriate gear box and also imbalances the bridge by an amount 1 proportional to the value of the particular digit. A motor is then energized and rotates the shaft until the bridge is balanced. This process is repeated for each digit of the number until the desired total number of rotations of the shaft has been achieved. The computer contains means for increasing or decreasing the total number of revolutions of the shaft, as measured from its zero or reference position, at any time by adding to or subtracting from the then existing total number of revolutions by the required amount.

A more detailed explanation of the invention will be given in connection with a specific embodiment thereof shown in the accompanying computer;

Figs. 3 and 4. show suitable forms of decoders for use in the computer Fig. 5 shows a suitable control amplifier for use in the computer; and

Figs. 6 and 7 shows specific examples of the I several codes necessary to produce a specified number of revolutions of the computer shaft.

Referring to Figs. 1a and lb the computer has input terminals I9 and an output shaft 5 I. Upon application of a coded electrical signal to terminals NJ the computer operates to produce the number of revolutions of shaft H specified by the signal. The revolutions of the shaft are produced in a series of steps, there being one step for each place in the decimal number expressing the desired number of revolutions. For example, if the desired number of revolutions is 126%, the computer produces 1000 revolutions of the shaft II in the first step, 200 revolutions in the second step. revolutions in the third step and a revolutions in the fourth step. The maximum number of steps is therefore determined by the maximum number of revolutions that the computer will be required to produce. The computer shown operates in four steps and is therefore capable of producing revolutions of shaft I l and a minimum of l to a maximum of 999.

The number of revolutions produced in each step is determined by the rotations of shaft If necessary to balance Wheatstone bridge I 2 which is mechanically coupled to the shaft and which has been unbalanced, in response to the coded signal, by an amount proportional to the number of revolutions of the shaft required in the particular step. The bridge [2 is composed of fixed arms I3 and I 4 and adjustable arms 55 and It. Arms l5 and [6 are identical, each being divided into nine equal sections by taps numbered 0 through 9. The arm I5 is connected to point ll of the bridge by rotating contact 16 which may engage any of the taps 0-9, while the arm I ii is connected to point ll by the upper contacts of whichever of relays i9 through 28 is actuated at the time. The bridge is energized by alternating voltage applied between points H and if, and the output is taken from points 39 and 3E. The use of alternating voltage allows the bridge to indicate the direction of unbalance by the phase of the output voltage.

The rotating contact I8 is mounted on shaft 29 which is mechanically coupled to shaft 3:; by gears 3| and 32. Shaft 30 may in turn be coupled to shaft ll through any one of four parallel paths. One of these paths comprises magnetic clutch 33, memory device 34, magnetic clutch and 10,000/1 gear box 36. The remaining three paths comprise. elements 3l383949, t! 42-fl344 and 454Ei 4l48. These elements are identical to the corresponding elements in the first described path with the exception of the gear boxes which have gear. ratios that are related to each other in multiples of 10, as indicated on the drawing. The total gearing between shaft l I is such that when the'10,000/1 gear box is engaged, 9000 revolutions of shaft II are required to move contact I8 of the bridge from tap to tap 9; whereas, for the 1000/1 gear box 900 revolutions are required, for the 100/1 gear box 90 revolutions are required, and for the 10/1 gear box 9 revolutions are required for the movement of contact I8 from tap 0 to tap 9.

Associated with each of the gear boxes 36, .40, 44 and 48 are decoders 49, 50, and 52, respectively, which, in the presence of an appropriate signal, operate through relay groups 53, 54, 55 and 56, respectively, to engage magnetic clutches 35, 39, 43 and 41, respectively, for coupling shaft II to shaft 29 through the appropriate ear box. The signal also contains information as to the number of revolutions required of shaft II during the time each of the gear boxes is engaged. This part of the signal operates through one of the digit decoders 5l66 to close one of the relays I9-28. This action connects the appropriate tap of resistor I6 to point I! of the bridge, and energizes relay coil I34 which engages one of the magnetic clutches 333'I--4I45 through contacts I33, depending upon which gear box is engaged at the time, and connects control amplifier 68 to the bridge through contacts 61. The output signal of the bridge then operates through control amplifier 68 to cause motor 69 to rotate shaft II in the proper direction to balance the bridge. This process is repeated for each of the gear boxes.

After shaft I I has rotated through the required number of revolutions for a particular gear box and after the signal has ceased, the bridge isreset to its zero position. This is accomplished by a torque producing device ll! coupled to shaft 29. In the embodiment shown I0 is a two phase motor. When polarized relay II is in the center position the motor I0 is deenergiaed. Application of voltage from terminal E, which in all occurrences in the drawing represents a source of power either A. C. or D. C. for operating the various relays, through reset interlock contacts I2, 73, i4 and "I5 and thence through limit switch "I6 to coil l? of relay "II closes the left-hand contacts of the relay 'II. This energizes motor 10 which drives the bridge contact I8 counterclockwise toward its zero position where it is stopped by limit switch l6.

As has already been pointed out the computer shown produces the desired number of revolutions of shaft II in four steps. In the first step the required number of thousands of revolutions are produced with gear box 36 engaged; in the second step the required number of hundreds of revolutions are produced with gear box 43 engaged; in the third step the required number of tens of revolutions are produced with gear box 44 engaged, and in the fourth step the required number of unit of revolutions are produced with. gear box 48 engaged. These revolutions of shaft II add to produce the required total number of revolutions as measured from the start or zero revolution condition of the shaft and as specified by the received signal. The signal applied to the computer always calls for a desired total number .of revolutions of the shaft. Consequently signals subsequent to the first may call for a greater or lesser number of total revolutions than did the first signal. The computer responds to these signals by adding to or subtracting from the existing total number of revolutions of the shaft by the amount required to produce the new total. Reduction of the total number of revolutions is accomplished by rotating theshaft backward.

coil I34.

Corrections in the total number of revolutions, as described above, require a means for resetting the bridge to the positions ofbalance which existed for thepreceding signal. Corrections are then made by driving the bridge through the appropriate gear box from the preceding position of balance tothe new position of balance called for by. the new signal. Such resetting of the bridge is accomplished by a memory device associated with each of the gear boxes, the rotating switch 18 associated with the adjustable arm of the potentiometer, and motor 10. Memory devices 34, 38, 42 and 4B are all identical. When the bridge is driven to a position of balance through one of the four gear boxe the two rotary switches of the associated memory device are also driven to a position corresponding to the balance point of the bridge. Upon receipt of the next signal engaging the gear box associated with the particular memory device that device operates to reset the bridge to the preceding position of balance if the signal has changed. 'If the signalis the ame as the precedingsignal no resetting-of the bridge takes place.

How the above is accomplished may be seen by referring to memory device 34. This device is associated with the 10,000/1 gear box'and comprises rotary switches 19 and 8!). Assume that the preceding signal for gear box 36 had caused the bridge to balance at tap 1. This resulted in switch 19 being moved to contact 1 and in switch being moved to such a position as to make contact with all contacts except 1 and beyond, as

shown in Figlb. With switch 80 in the position shown, segment 0 of switch 18 is energized through switch BI. Since the bridge arm I8 and switch i8 have been previously reset to, their zero positions, voltage is applied through segment 0 and the arm of switch 18, through interlockcontacts 82, 83, 84 and 85 of relay groups 53, 54, 55 and 56, and through the lower contacts of whicheverof digit relays I9"28 was actuated by the newsignal, to coil 86 of relay II. This actuates relay II to the right causing motor-Ill to drive the bridge contact I8 and switch I8 in a clockwise direction. Thiscontinues until the contact of reset, contacts 8'! close and voltage is applied through interlock contacts 88, interlock contacts 81, and the middle contacts of whichever of digit relays I 9-"'3 has been closed by the signal, to Energization of coil I34 applies voltage to clutch 33 through contacts I33 and switch 8I and applies the output voltage of the bridge to phase sensitive control amplifier 58 through contacts 61, which, causes motor 69 to rotate shaft II in the proper direction to balance the bridge which is now coupled to shaft Ilthrough magnetic clutch ,33, memory device 34, magnetic clutch 35 and gear box 33. Since the memory device is a part of, this coupling train it is reset in the process to the new position of balance .of the bridge.

The function of switch ,79 is to prevent the needless resetting of the bridge to its-previous balance position in the eventthat the new signal is the same as the preceding, signal. Referring again to memory device 34 and assuming that the bridge had been previously balanced at 1, as shown by the fact the switch 19 is on contact 1, and that the new signal is the same as the preceding signal and therefore is passed by digit decoder 58 for the purpose of actuating digit relay associated with tap 1 of the bridge arm 16. If relay 29 were allowed to close coil 86 of relay H would be energized and the. bridge arm 18 needlessly moved to tap 1. This is prevented, however, by switch "iil'which applies a voltage through contact 1 thereof and switch I00 to coil I28 which opens contacts I29 thereby preventing closure of relay 2B. The remaining relays'likerelay l28 i 29 are associated with the remaining digit relays and the remaining contacts on switch 19 for the same purpose.

The memory device 34 also contains areset mechanism comprising pinion 89, rack 90 and solenoid 9|. This mechanism functions only in initiating operation of the computer, at which time a start signal energizes solenoid 9| and resets the memory device to zero. Remaining memory devices 38, 42 and 46 are identical in construction and operation to device 34'. Switches I03, 84, I05 are associated with memory devices 38, 42 and 46 in the same manner as switch 8| is associated with device 34, and, similarly, switches Hit, IE1, IE8 bear the same relationship to these ievices as switch I06 does to memory device 34.

The motors 69 and 10 may be any suitable reversible motors with appropriate control circuits. In the embodiment illustrated these are shown as two-phase motors with a center-tapped transformer and relay used to invert one of the phases for reversing the motor. The operation of relay i'i has alreadybeen explained. Relay 32 is similar to relay H in operation. Energization of coil 93 operates relay 92 upward for retation in one direction and energization of coil 94 operates the relay downward for rotation in the opposite direction. When the relay is in its neutral or center position the motor is deenergized. Both motors 69 and 10 should have provisions, either electrical or mechanical, for stopping rotation immediately upon deenergization. Since a number of means for accomplishing this result are known and since this feature does not form a. part of the invention no specific braking mechanism. is illustrated.

The output voltage of the bridge will be in phase with or 180 out of phase with the energizing voltage depending upon the direction of unbalance. The control amplifier 6B compares the phases of these two voltages and energizes the proper one of coils 92. and 93 to produce rotation of shaft II in the direction required to balance the bridge. A suitable amplifier for this purpose is shown in Fig. 5. Theenergizing voltage of the bridge is also applied through transformer 95 to the anodes of tubes 96 and 91 in the same phase, while the output voltage of the bridge, after am lification by tube 98, is applied to the grids of tubes 96 and 91 in opposite phase. Therefore, the voltages on the anode and grid will be in phase in one of tubes 96 and 91 and 180 out of phase in the other tube. By properly biasing the grids of the tubes there will be no current flow in the anode circuit of the tube in which the voltages are of opposed phase, while a flow of current sufiicient to operate relay 92 will flow in the anode circuit of the tube in which the anode and grid voltages are of the same phase. In the absence of an output signal from the bridge there will be no signal on the grids of 6 tubes 96 and 91 and consequently the anode cur rents will be equal and relay 92 will not be actuated. These latter currents may be made very small or even zero by applying sufiicient bias to the grids of the tubes.

The decoder 99 may be termed the start decoder. It responds to a start signal to zero the memory devices 34, 38, 42 and 46 and to open interlock contacts 82, 83, 84 and 85. The decoders 49, 50, 5! and 52 may be termed the thousands, hundreds, tens and units decoders, respectively, and in effect, they represent the four places of a four-place decimal number. These decoders respond, respectively, to signals calling for engagement of the 10,000/ 1, the 1000/1, the 100/1 and the 10/1 gear boxes. Decoders 5'|6B are digit decoders which respond to signals specifying the proper digit for each of the four places of the decimal number represented by the decoders 49, 50, 5| and 52.

The coded signal is applied to terminals i0 and through amplifier and shaper I09 to the inputs of the decoders in parallel. The amplifier and shaper I09 may be any suitable amplifier and clipping or limiting device to insure that the signals applied to the decoders will be of uniform amplitude and form so as to avoid any erratic operation of the computer from this source.

The ten position binary code used with the computer is shown in Fig. 2. The start signal is shown in the first line and consists of three pulses occupying the first three positions of the code. All signals applied to the computer other than the start signal are in the nature of a combined signal in which the first pulse and the second pulse determine which of the four gear boxes is to be engaged and in which the first pulse together with the third pulse or, in some cases, the third and fourth pulses, determine which of the digit relays ill-28 is to be actuated. All the required pulse combinations are indicated in- Fig. 2 in which the two pulses to the left of the center line constitute the gear box signal and the first pulse to the left of the center line together with the pulse or pulses to the right of the center line constitute the digit signal. For example, if the 1000/1 gear box and digit relay 25 corresponding to the digit 6 are to be actuated the required signal would contain pulses at positions 1, 3, 6 and 7.

From Fig. 2 it is apparent that decoder 9?! must be a three pulse decoder, decoders 49, 50, 5| and 52 must be two pulse decoders, decoders 58, 59, 60, SI and 62, corresponding to digits 1, 2, 3, 4 and 5, must be two pulse decoders, and decoders 63, 64, 65, 66 and 57, corresponding to digits 6, '7, 8, 9 and 0, must be three pulse decoders. A suitable two pulse decoder is shown in Fig. 3. this circuit tube 10 is so biased that it will conduct only in the presence of positive pulses on grids Ill and H2 simultaneously. The signal is applied from input terminals H3 directly to grid Ill and through delay line ll l to grid H2. If the delay produced by line I M is exactly equal to the interval between the two pulses of the signal the first pulse will arrive at grid H2 at the same time that the second pulse arrives at grid ill and plate conduction will occur. If the separation of the pulses differs from. the delay of the line concurrence of the pulses will not occur. Tubes H 5 and H6 are direct current amplifiers and circuits H1, H8 and H9 are integrating networks to produce a steady output in the presence of a repeated two-pulse signal.

spacers 7 A suitable three-pulse decoder is shown in Fig. 4. This decoder operates on the same principle as that in Fig. 3. The tube contains three instead of two grids and'pulses must be appliedsimultaneously to all three grids to cause plate con-,.

duction. To accomplish this the delay of the entire transmission line is made equal to the time interval between the first and third pulses while the delay of that partof the linewbetween grids I28 and I2I is made equal to the interval between the first and second pulses. This .results in the simultaneous appearances of the first pulse on grid I22, the second pulse on grid. I2I and. the first pulse on grid I20.

The preceding descriptive matter has dealt with the construction and operation of the principal components of the computer. The opera.- tion of the computer as a whole can best be demonstrated by a specific example. Assume that it is desired to producel264 revolutions of shaft I I as measured from its zero position. The necessary signals, derived from Fig. 2, are shown in Fig. 6. Five distinct signals marked (a) through (c) are required. Each of these signals is transmitted to the computer repeatedly for. a-

set to zero when power is applied to the.com-

puter by voltage applied from E through contacts I2, I3, I4, I5 and I6 to the zero reset coil II of relay II. The first signal to be applied to terminals I0 of the computer is start signal (a) of Fig. 6. This signal produces a direct output current from decoder 99 which closes contacts I23 of relay group 53 and the corresponding con tacts in identical relay groups 54, 55 .and 55. Closure of contacts I23 closes contacts I24 and opens contacts 82. Closure of contacts I24 applies voltage from E to the coil of this relay which will hold contacts 82 open after contacts I23 have been released at the end of the start signal. In a similar manner contacts 83, 84 and 85 of relay groups 54, 55 and 56 are opened and held open. Closure of contacts I23 also applies voltage to reset solenoid 9I which resets memory device 34 to zero. In a similar manner memory devices 38, 42 and 46 are reset to zero. The function of the start signal; therefore, isto reset the memory devices to zero and to openinterlock contacts 82, 83, 84 and 85. Opening of these contacts prevents energization of coil 86 of relay II until initial operation through each of the four gear boxes has taken place.

The next signal applied to the computer is the signal (12). The first two pulses from this signal produce an output from decoder 49 which opens contacts I2 and closes contacts I25. Closure of contacts I25 results in closure of contact I26 and opening of contact I2I thus trans- Ierring the holding circuit for contacts 82 and I24 from contact I2I to contact I26. In order to prevent opening of contacts I24 and the resulting closure of contacts 82 by this transfer this relay is of the delayed release type as indicated by the symbol DR. Closure of contacts I25 also energizes magnetic clutch 35, switch BI and switch I00.

The first and third pulse of signal (b) produce an output from digit decoder 58 which actuates digit relay 20, the upper contacts of which Closure of the middle contacts of relay netici clutch 33.

Lzero .and rotation 'of' motor '69 ceases.

Closure :of contacts 61 applies the output signal of the bridgeto control amplifieriB which causes motor 69 to rotate shaft II and to drive contact I8 of the bridge in a clockwise direction'through'the 10,000/1 gearbox and *memoryxdevice 34. 'When contact I8 reaches I3. and 80 ef-the memory device 34 along with s the bridgeito' th'eir'iil positions. Voltage from '.E.is applied throughswitch I9, conductor 1 and switch lllll'to'coil I28 thusopening'contacts. I28

and deenergizing relay 20. Opening f the mid dle contacts of relay deenergizescoil I34 thus "releasing magnetic clutch33 and disconnecting amplifier I58 from the bridge by opening contacts I33sand 61. Energization of coil 85 of relay .II through :switches and :18 however, .is not possible since contacts 82; 83, 84 and 85 are open.

Cessation of signal (1)) reduces theoutput-oi decoder 49 to zero closing contacts I2 and opening contacts I25. coil 11 of relayIIand resets the bridge to zero.

Closureof contacts I2 energizes Resetting-of :the bridge doesnotaffect the setting .of memorydevice 34 since clutch 33 is released.

tact isaof. the delayed closing type asindicated by thesymbol DC. Opening of contacts I25 also releases magnetic-clutch 35 and switch 8|. This completes the first step in the initial-cycle of op- '40 eration of the computer. One thousand of-the required 1264 revolutions were imparted to shaft I I in this step.

The second step in the cycle is initiated by the application of signal (0) of Fig. 6 to the terminals I0 of'the computer. Theoperation of thecomputer inthe second steptis identical with that in the" first stepz'described' above and results .in 200 more of the: required 1264 revolutions of shaft I l. The first two pulses of signal (0) acting through decoder 50 cause engagement of the1000/ 1 gear box. and the first and third pulses of this signal 'act. through digit decoder 59.:to energize digit relay 2| and connect tap 2:0f resistor I5 to point H of the bridge. Motor BSAacting through'shaft II and the 1000/1 gear box movescontact I80f the bridge from tap 0 totap 2 where the bridge balances. This requires 200 revolutions of shaft The'third-and fourth steps of operation 'result from signals (d) andie) respectively. The third step involves /1 gear box 44 anddigit relay 25,

- and results in '60'more' revolutions of. shaft II bringingthe total number of revolutions at this point to 1260. The fourth and final step'of operation involves the 10/1 gear box 48 and digit relay 23, and results in four additional revolutions of shaft I I making the final total 1264 as required. The operation ofthe computer in the third. and

fourth steps is "identical with "its operation in the first step.

At any time "after the initial cycle of operation described above has been completed the computer is ready to receive new'signals callingfor total revolutions of shaft II greater or less than'the then existing total: number of revolutions. Ifthe required total number is greater than the existing number of revolutions the computer rotates the shaft forward through the necessary number of revolutions to build the existing total up to the required new total. If the new signal calls for a total number of revolutions less than the then existing total the computer rotates the shaft backward the necessary number of times to reduce the existing total to the required new lower total. This type operation also can best be explained by a specific example. Assume that the next signal to be received following the initial signal calls for a total number of revolutions of shaft I I of 1243, requiring that the shaft be rtated backward through 16 revolutions to reduce the existing total of 1264 to the new total of 1248. The complete signal in this case is shown in Fig. '7.

The first two parts of the new signal, marked (b) and (c') in Fig. '7, are the same as the first two parts (1)) and (c) of the initial signal shown in Fig. 6, since no change in the thousands place or the hundreds place of the total is required. The response of the computer to signals (b') and (c) is as follows: The application of signal (2)) to the computer produces an output from gear box decoder 49 and digit decoder 58. The output from decoder 49 closes contacts I25 which applies voltage to and closes switch I00. In the first step of the initial cycle of operation of the computer, switch I9 of memory device 34 was positioned on contact 1 and it is still in this position. Closure of switch I88 therefore causes a voltage to be applied from E through contact 1 of switch It! and through switch I00 to coil I28 thus opening contacts I28 in series with the coil of digit relay and preventing actuation of this relay by the output voltage of decoder 58. In order to insure opening of contacts I 29 before actuation Of relay 2! can take place this relay is of the delayed actuation type as indicated by the symbol DA. Since relay 20 is thus prevented from closing relays coils I34 and 86 can not be energized and no rotation of shaft II by motor 89 or resetting of the bridge by motor I0 can take place. The computer remains in this inactive state until signal (1)) ceases, at which time contacts I and switch I88 open. The response of the computer to the signal (0) is exactly like its above described response to signal (1)) except that in this case decoder 48, decoder 58, memory device 38, relay group 54 and switch I86 are involved. As in the case of signal (1)) no revolutions of shaft II are produced by signal (0) and also no resetting of bridge I2 takes place.

The third part (i) of the new signal however differs from the third part (d) of the initial signal in calling for 40 revolutions of shaft I I whereas the initial signal called for revolutions. The computer, therefore, must respond to signal (I) to rotate shaft II backward through 20 revolutions. This is accomplished as follows: Application of signal (7) to the computer produces output voltages from gear box decoder 5| and digit decoder BI. 5| closes contacts I30 and opens contacts I4. Closure of contacts I38 engages magnetic clutch 43 and closes switches I04 and H11. Memory device 42 was set during the initial cycle of operation of the computer so that switch I3I rests on contact 6 and switch I32 makes connection to all contacts below 6, corresponding to the balance point of bridge I2 in the third step of the initial cycle of operation of the computer. At this time contact l8 0f the bridge and the The voltage from decoder rotating contact of switch I8 are in their zero positions.

Segments 0-5 of rotary switch I8 are energized by connection through switch I04 to contacts 0-5 of switch I32 in memory device 42. Closure of digit relay 23 by the output voltage of decoder BI therefore causes voltage to be applied through the moving contact of switch I8; contacts 82, 83, 84 and 85, and the lower contacts of digit relay 23 to coil 86 of relay II. Energization of coil 86 opens contacts 81 which removes the voltage that was applied to coil I34 from E through contacts 88, 8! and the middle contact of relay 23 when this relay closed. In order to insure that contacts 81 and I33 do not close before contacts 8! have had time to open a delayed actuation type relay is used as indicated by the symbol DA.

Energization of coil 86 operates relay II to the right causing motor III to rotate switch I8 and bridge contact I8 clockwise. This rotation continues until the moving contact of switch I8 reaches the first deenergized segment which in this case is segment 6. At this point coil 88 is deenergized and motor Ill stops. Contact I8 of the bridge has now been reset to tap 6 which was the balance point in the third step of the initia cycle of operation.

Removal Of voltage from coil 86 allows contacts 81 to close thus applying voltage through the middle contacts of digit relay 23 to coil I34 and closing contacts I33 and 81. Closure of contacts I33 energizes magnetic clutch 4I through switch I94, while closure of contact 8! applies the output of the bridge to control amplifier 88. Since the balance point of bridge I2 is now at tap 4 whereas the contact I8 is at tap 6, the phase of the output voltage will be reversed with respect to previously considered cases. The reversed phase output voltage operates through phase sensitive control amplifier 68 to cause reversed rotation of motor 69 and shaft II. Since bridge contact I8 is now coupled to shaft II through clutches II and 43, memory device 42 and /1 gear box 44 the contact is rotated in a counterclockwise direction until it reaches tap 4 at which point the bridge balances and its output becomes zero, resulting in deenergization of motor 39. Also, when the bridge balances, the moving contact of switch I3I in memory device 42 has reached contact 4 which results in a voltage being applied through switch NJ! to coil IDI, opening contacts I82 and deenergizing digit relay 23. Opening of the relay contacts deenergizes coil I34 and opens contacts 6! and I33 which disconnects the bridge from amplifier 68 and releases magnetic clutch 4|. No further action takes place until signal (2) ceases, at which time contacts I38 open and contacts I4 close. Opening of contacts I33 releases magnetic clutch 43 and switches I84 and I 81. C10- sure of contacts I4 resets the bridge to zero, terminating the third step in the cycle of computer operation. In moving the bridge from tap 6 to tap 4 through the 100/1 gear box the shaft I I reduced its total number of revolutions by 20.

The last of the four steps in this cycle is initiated by the signal (9) of Fig. '7. Like signal (1) this signal diifers from the signal in the fourth step of the preceding cycle of operation of the computer, calling for eight revolutions of the shaft as compared to four in the initial cycle. The computer therefore must operate to rotate the shaft forward through four revolutions to raise the number in this step from four to eight.

The response ofthe computer to signal (9 is similar in all respects to its response to signal (f) described in detail above. The signal acts through decoders 52 and 65 to engage the /1 gear box 48 by actuating magnetic clutch 4! and to close digit relay 21. The memory device 46, which still has the position to which it was set in the fourth step of the initialcycle of opera:- tion, acts through rotary switch 18 and motor IE! to reset the bridge to tap 4. Motor 69 is then energized and rotates bridge contact [8 in a clockwise direction through shaft ll, gear box 48 and memory device 46 until the bridge balances at tap 8. Moving arm l8 from tap 4 to tap 8 though the 19/1 gearbox requires 4 revolutions of shaft H.

In the third and fourth steps in this cycle of operation the computer responded to signal (1) to rotate the shaft I I' backward through 20 revolutions and responded to signal (g) to rotate the shaft l l forward through i revolutions. The net result of the entire signal of Fig. 7 therefore was a backward rotation of shaft I l of i6 revolutions which reduced the previous total of 1264 revolutions to the required new total of 1243 revolutions. Any number of signals of the type shown in Fig. '7 may be applied in succession to the computer. The computer will respond to each of these signals to change the total number of revolutions of the shaft ll to the number specified in the signal by adding to or subtracting from the existing total number of revolutions of the shaft by the required amount in the manner described above.

I claim:

1. A computerfor converting a coded electrical signal into a specified total number of revolutions of a shaft as measured from a start or zero revolution position thereof, said signal having a plurality of successively occurring parts each corresponding to one place of the decimal number representing the maximum total number of shaft revolutions of which the computer is capable, said computer comprising a shaft, a reversible motor coupled to said shaft for rotating it in eitherv direction, a Wheatstone bridge comprising two branch circuits connected in parallel each consisting of a fixed resistance arm and an adjustable resistance arm connected in series, each of said adjustable arms being divided by ten taps into nine equal parts, means for applying an energizing voltage to said bridge across said its driving side selectively coupled through a corresponding bridge coupling means to the adjusting mechanism of one of the adjustable arms of said bridge, the ratio of the gear box corre sponding to the lowest ordered place of said decimal number being such that nine revolutions of said shaft are required to adjust said one adjustable arm from zero to maximum resistance,

the ratios of the remaining gear boxes being equal to a multiple of ten times the ratio of said lowest ordered gear box, an equal number of gear box decoders each corresponding to one of said places in said decimal number, means responsive to an output signal from any of said gear box decoders to couple thedriving side of the corresponding gear box through the corresponding bridge coupling means to said one adjustable bridge arm,-

ten digit decoders each corresponding to one of the taps on theother of said adjustable bridge arms, means responsive to an output signal from any of said digit decoders to connect the corresponding tap of said other bridge arm to said bridge circuit and to connect the output circuit:

of said bridge to said control circuit, for energizing and controlling the direction of rotation of said motor, for'the purpose of driving the adjusting mechanism of said one adjustable; arm through the appropriate gear box and bridge coupling means to balance said bridge, and meansrecorded by said memory device, and means operative at the completion of said resetting to couple said shaft to said one adjustable bridge arm through the corresponding bridge coupling means and to apply the output of said bridge to said motor control circuit for adjusting said bridge from the said last recorded position of balance to a new position of balance as called for'by the existing signal.

3. Apparatus as claimed in claim 2 in which means are provided for preventing the-application of the output signal of said bridge to said control circuit during the resetting of said bridge to a recorded balance point. i

4. Apparatus as claimed in claim 3 in which means are provided for preventing the energization of the recorded balance point resetting olements until an initial output signal has occurred from all gear box decoders.

5. Apparatus as claimed in claim 4 in which said coded electrical signal is preceded by a start signal and in which a start decoderis-provided for. producing an output signal in response to said start signal, and means responsive to the output signal from said start decoder to reset all said memory devices to zero and to set said means for preventingenergization of the recorded balance point setting elements.

6. Apparatus as claimed in claim 5 in which means, responsive to the termination of any output signal from any gear box decoder, are provided for resetting said one adjustable bridge arm to zero.

LUDLOW B. HALLMAN, JR.

Number Name Date Seid Jan. 9, 1951'. 

